Mechano-chemical feedback leads to competition for BMP signalling during pattern formation

Abstract

Developmental patterning is thought to be regulated by conserved signalling pathways. Initial patterns are often broad before refining to only those cells that commit to a particular fate1,2. However, the mechanisms by which pattern refinement takes place remain to be addressed. Using the posterior crossvein (PCV) of the Drosophila pupal wing as a model, into which bone morphogenetic protein (BMP) ligand is extracellularly transported to instruct vein patterning3,4, we investigate how pattern refinement is regulated. We found that BMP signalling induces apical enrichment of Myosin II in developing crossvein cells to regulate apical constriction. Live imaging of cellular behaviour indicates that changes in cell shape are dynamic and transient, only being maintained in those cells that retain vein fate after refinement. Disrupting cell shape changes throughout the PCV inhibits pattern refinement. In contrast, disrupting cell shape in only a subset of vein cells can result in a loss of BMP signalling. We propose that cell shape changes of future PCV cells allow them to compete more efficiently for basally localised BMP signal by forming a mechano-chemical feedback loop. This study highlights a new form of cell competition: competing for a signal that induces cell fate rather than promotes cell survival.